Brian looks into the bottom draw in the kitchen, and right at the back finds.. a key. It looks familar, he's sure it used to be a regular companion, but he's got no idea what it's for. So he throws it away.

Well, he doesn't really. No one ever does, they just keep these key orphans for ever, not wanting
the karma problems of disposal. Instead, he snaps a photo of it and uploads it to Lockfinder ! quick as a flash, the site reminds him it's a key for a filing cabinet.